That incident prompted a wave of media inquiries into what's going on with his stomach. While Messi, his coaches, and his doctors have thrown out a bunch of different theories, there isn't one clear explanation.

"One cause can be physical and/or mental strain. The change in time zones — jet lag — and changes in diet also take a toll. Sometimes when people change their eating habits, it can trigger intolerance, leading to nausea and vomiting."

Messi himself called it "no big deal," saying, "Sometimes I accelerate very fast and the change in air intake causes me to heave. I felt completely fine at the end of the match"

It appears to be a strange but harmless ailment, but it happens all the time.